Low-resistance composite current collector with preset integrated tab and preparation method of low-resistance composite current collector

Abstract

The invention relates to the technical field of lithium battery materials, in particular to a low-resistance composite current collector with a preset integrated tab and a preparation method thereof.The low-resistance composite current collector with the preset integrated tab comprises a base film, and a metal foil is arranged at the end of the base film; the base film comprises a first area closest to the metal foil and a second area farthest from the metal foil, the first area and the second area are each provided with a plurality of holes penetrating through the base film in the thickness direction, and the density of the holes in the first area is larger than that of the holes in the second area. And a bottom layer and a metal layer are sequentially arranged on the side surfaces of the base film and the metal foil. According to the invention, through the near-dense and far-sparse gradient hole design, the current density distribution when the pole piece works is actively matched, an ultra-low resistance channel is provided in the first region where the current converges, and the ohmic polarization and heating of the region are significantly reduced.

Description

Technical Field

[0001] This invention relates to the field of lithium battery materials technology, specifically to a low-resistance composite current collector with pre-installed integrated tabs and its preparation method. Background Technology

[0002] Current collectors are the core components in a battery system that carry the active materials of the electrodes and collect current. In lithium-ion batteries, aluminum foil is used as the positive electrode and copper foil as the negative electrode, both traditionally used as current collector materials.

[0003] However, aluminum is relatively soft, and its surface oxide film makes electrode tab welding extremely difficult, resulting in low yield. At the same time, positive electrode active materials, such as high-nickel ternary and lithium iron phosphate, have poor conductivity and rely more on low-resistance current collectors to reduce polarization. The high resistance of traditional composite aluminum foil severely restricts its application in high-voltage and high-energy-density batteries. Traditional composite copper foil is thin, which makes it easy to have problems such as poor welding and melting through the base film when welding copper tabs, resulting in poor connection reliability. At the same time, the thin copper layer leads to excessively high surface resistance and high battery internal resistance, which cannot meet the requirements of fast charging and high-power scenarios. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of high point resistance and difficult welding of traditional composite current collectors, and to provide a low-resistance composite current collector with pre-installed integrated tabs. The denser holes near the current and sparser holes at the far end ensure the reliability of the electrical connection while reducing the resistance in the key area where the current converges.

[0005] To achieve the above objectives, the present invention provides a low-resistance composite current collector with a pre-installed integrated tab, comprising a base film, wherein a metal foil is disposed at one end of the base film, and the base film includes a first region closest to the metal foil and a second region farthest from the metal foil along a direction perpendicular to the metal foil. Both the first region and the second region are provided with a plurality of holes penetrating the thickness of the base film, and the density of holes in the first region is greater than the density of holes in the second region. The base film and the metal foil are sequentially provided with an underlayer and a metal layer for connecting the base film and the metal foil into one unit.

[0006] Preferably, the density of holes in the first region is set to 2,000-50,000 per square centimeter, and the density of holes in the second region is set to 50-2,000 per square centimeter.

[0007] Preferably, a third region is provided between the first region and the second region, and the third region is provided with multiple rows of holes. The density of holes in the third region is less than the density of holes in the first region but greater than the density of holes in the second region.

[0008] Preferably, each side of the base film and the metal foil is provided with the underlayer and the metal layer, the underlayer and the metal layer covering the inner wall of the hole to connect the underlayer and the metal layer located on the two opening surfaces of the hole.

[0009] Another aspect of the present invention provides a method for preparing the above-mentioned pre-embedded integrated electrode tab low resistance composite current collector, comprising gradient perforation of a first region, a second region and a third region on a base film, attaching a metal foil with an adhesive layer to the electrode tab region on the base film, and then depositing an underlayer and a metal layer on the sides of the base film and the metal foil.

[0010] Preferably, a laser is used to perform gradient laser drilling on the first, second, and third regions of the base film.

[0011] Preferably, when drilling the first region, the laser beam is controlled to perform scanning drilling with a pulse frequency of 200-500 kHz and a scanning interval of 5-10 μm.

[0012] Preferably, when drilling the second region, the laser beam is controlled to perform scanning drilling with a pulse frequency of 50-150 kHz and a scanning interval of 50-100 μm.

[0013] Preferably, when drilling the third region, the laser beam is controlled to scan and drill along the direction from the first region to the second region, with the scanning distance from the first region gradually increasing to the scanning distance of the second region for each row.

[0014] Preferably, the pulse energy of the laser is 0.1-2 mJ.

[0015] Compared with the prior art, the technical solution provided by this invention reduces the sheet resistance of the composite current collector through the porous structure. At the same time, the gradient porous design with denser holes near the surface and sparser holes at the far end actively matches the current density distribution when the electrode is working, providing an ultra-low resistance channel in the first region where the current converges. This significantly reduces ohmic polarization and heat generation in this region, thereby improving the overall rate performance, cycle life and thermal safety of the battery. Attached Figure Description

[0016] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts. Wherein:

[0017] Figure 1 This is a schematic cross-sectional view of a low-resistance composite current collector with a pre-installed integrated tab, provided by the present invention.

[0018] The diagram is labeled as follows: 1. Base film; 2. Metal foil; 3. Adhesive layer; 4. Underlayer; 5. Metal layer; 6. Hole. Detailed Implementation

[0019] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0020] This invention provides a specific embodiment of a low-resistance composite current collector with a pre-installed integrated tab, such as... Figure 1 As shown, the composite current collector includes a base film 1 and a pre-placed metal foil 2. The base film 1 is divided into a tab region, a first region, a third region, and a second region along its width direction. An adhesive layer 3 is provided on the metal foil 2. The metal foil 2 is placed at the tab region at the end of the base film 1 through the adhesive layer 3. The adhesive layer 3 is formed by the curing of conductive adhesive, which eliminates the need for welding and avoids the trouble caused by welding. The first region, the second region, and the third region are connected, and a gap is left between the first region and the tab region.

[0021] Multiple rows of holes 6 penetrating the thickness of the base film 1 are respectively provided in the first, second, and third regions. Each side of the base film 1 and the metal foil 2 is provided with a substrate 4 and a metal layer 5. The substrate 1 and the metal foil 2 are connected as one unit through the substrate 4 and the metal layer 5. The integrated connection has no welding weaknesses, which can improve battery safety. The substrate 4 and the metal layer 5 cover the inner wall of the holes 6 to connect the substrate 4 and the metal layer 5 located on the two opening surfaces of the holes 6, so that the substrate 4 and the metal layer 5 on both sides form a parallel conductive network in three-dimensional space, which significantly reduces the sheet resistance. It should be noted that the substrate 4 and the metal layer 5 can be provided only on one side of the base film 1 and the metal foil 2, which is not limited here.

[0022] The density of holes 6 in the first region is greater than that in the third region, and the density of holes 6 in the third region is greater than that in the second region. The spacing between adjacent rows of holes 6 in the third region increases along the direction from the first region to the second region. The spacing between adjacent rows of holes 6 in the third region that are closer to the first region is smaller than the spacing between adjacent rows of holes 6 that are farther away from the first region. The density of holes 6 in the third region gradually changes, thus achieving a smooth transition from the first region to the second region. At the same time, the sheet resistance of the composite current collector is reduced through the holes 6.

[0023] The aperture of the holes 6 is set to 2-300μm, and the density of the holes 6 in the first region is set to 2000-50000 per square centimeter to maximize the conductive channels and efficiently collect current. The density of the holes 6 in the second region is set to 50-2000 per square centimeter to optimize the processing efficiency and strength of the base film 1 while ensuring conductivity and maintaining the overall mechanical properties of the current collector.

[0024] By designing a gradient of denser holes near the surface and sparser holes further away, the current density distribution during electrode operation is actively matched. In the critical area where current converges, namely the first region, an ultra-low resistance channel is provided, which significantly reduces ohmic polarization and heat generation in this region, thereby improving the overall rate performance, cycle life and thermal safety of the battery.

[0025] Another aspect of the present invention provides a method for preparing the above-mentioned pre-embedded integrated tab low-resistance composite current collector, including using a laser to perform gradient laser drilling on a first region, a second region and a third region on a base film 1, the pulse energy of the laser being 0.1-2 mJ, attaching a metal foil 2 with an adhesive layer 3 to the tab region on the base film 1, and then depositing an underlayer 4 and a metal layer 5 on the sides of the base film 1 and the metal foil 2.

[0026] Example 1

[0027] This embodiment is used to prepare a low-resistance composite copper foil with pre-installed integrated tabs. In this embodiment, the metal foil 2 is pure copper foil. The pure copper foil is cut into the required tab width rolls and then installed on the unwinding device. The surface is cleaned and activated by a plasma cleaner or UV ozone treatment equipment to improve its surface adhesion. The coating is carried out by slit extrusion coating or micro-gravure roller coating process. Both of these methods can achieve high precision and large-area uniform coating. The conductive adhesive is delivered to the coating head by a metering pump to ensure that a uniform and continuous wet film is formed on the surface of the pure copper foil. The coated pure copper foil is guided through a 5-10 meter long tunnel oven and dried and cured under a temperature curve of 80℃-120℃-150℃ to allow the solvent to fully evaporate and the conductive adhesive to be completely cured and form a strong bond with the pure copper foil to form adhesive layer 3.

[0028] The base film 1 is fed into the roll-to-roll laser equipment. When drilling the first region, the laser beam is controlled to scan and drill with a pulse frequency of 200-500kHz and a scanning interval of 5-10μm to form holes 6 with extremely high density. When drilling the second region, the laser beam is controlled to scan and drill with a pulse frequency of 50-150kHz and a scanning interval of 50-100μm. When drilling the third region, the laser beam is controlled to scan and drill along the direction from the first region to the second region, with the scanning interval gradually increasing from the first region to the second region.

[0029] The base film 1 is fed to the main unwinding shaft of the roll-to-roll bonding machine, and the pure copper foil tabs with adhesive layer 3 are fed to the auxiliary unwinding shaft. After adjusting to meet the accuracy requirements, high-temperature bonding begins, and the temperature of the bonding roller is set to 95-105℃.

[0030] The attached material is fed to a roll-up magnetron coating machine to perform copper plating on the A / B sides as a base layer. Each of the A / B sides is plated with copper with a thickness of 70-90nm as the base layer 4. Then the roll film is fed to the water plating line, and the base layer 4 on the A / B sides is water-plated to thicken it, i.e., the metal layer 5. The copper layer is thickened until the total thickness of the base layer 4 and the metal layer 5 on one side is 1μm.

[0031] The pre-placed pure copper foil and the base film 1 form a solid integrated structure, completely avoiding all defects of the post-welding process, clearing the biggest obstacle for the large-scale application of composite copper foil. The holes 6 reduce the sheet resistance of the composite copper foil by 30%-60%, making its conductivity meet the requirements of fast charging of the negative electrode. The integrated connection has no welding weaknesses, and combined with the melting characteristics of the composite copper foil itself, it doubles the improvement of battery safety.

[0032] Example 2

[0033] This embodiment is used to prepare a low-resistance composite aluminum foil with pre-installed integrated tabs. In this embodiment, the metal foil 2 is pure aluminum foil. The pure aluminum foil is cut into the required tab width rolls and then installed on the unwinding device. The surface is cleaned and activated by a plasma cleaner or UV ozone treatment equipment to improve its surface adhesion. The coating is carried out by slit extrusion coating or micro-gravure roller coating process. Both of these methods can achieve high precision and large-area uniform coating. The conductive adhesive is delivered to the coating head by a metering pump to ensure that a uniform and continuous wet film is formed on the surface of the pure aluminum foil. The coated pure aluminum foil is guided through a 5-10 meter long tunnel oven and dried and cured under a temperature curve of 80℃-120℃-150℃ to allow the solvent to fully evaporate and the conductive adhesive to be completely cured and form a strong bond with the pure aluminum foil to form adhesive layer 3.

[0034] The base film 1 is fed into the roll-to-roll laser equipment. When drilling the first region, the laser beam is controlled to scan and drill with a pulse frequency of 200-500kHz and a scanning interval of 5-10μm to form holes 6 with extremely high density. When drilling the second region, the laser beam is controlled to scan and drill with a pulse frequency of 50-150kHz and a scanning interval of 50-100μm. When drilling the third region, the laser beam is controlled to scan and drill along the direction from the first region to the second region, with the scanning interval gradually increasing from the first region to the second region.

[0035] The base film 1 is fed to the main unwinding shaft of the roll-to-roll bonding machine, and the pure aluminum foil tabs with adhesive layer 3 are fed to the auxiliary unwinding shaft. After adjusting to meet the accuracy requirements, high-temperature bonding begins, and the temperature of the bonding roller is set to 95-105℃.

[0036] The attached material is fed to a roll-up magnetron coating machine to deposit aluminum oxide base layer on both sides A and B. Each side A and B is coated with 20-40nm thick aluminum oxide as the base layer 4. Then the roll film is fed to an evaporative aluminum coating machine to deposit aluminum layer on the base layer 4 on both sides A and B to thicken it, i.e., metal layer 5. The aluminum layer is thickened until the total thickness of the base layer 4 and metal layer 5 on one side is 1μm.

[0037] The pre-installed integrated aluminum tab provided in this embodiment perfectly avoids the process difficulties of aluminum welding, and provides the only reliable connection solution for the application of composite aluminum foil in the positive electrode. The reduced resistance helps to reduce the polarization of the battery under high voltage, improve the platform voltage and energy efficiency, and make the composite aluminum foil applicable to high voltage platforms of 4.5V and above. In addition, this design is particularly beneficial for high current charging and discharging scenarios, because the current density is the largest in the area near the tab at this time, and the first area can effectively alleviate the current congestion effect here.

[0038] The low-resistance composite copper foil and low-resistance composite aluminum foil with pre-installed integrated tabs provided in the above two embodiments can realize the solderless manufacturing of all tabs in the battery cell, leading to the innovation of battery manufacturing process.

[0039] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A low-resistance composite current collector with a pre-installed integrated electrode tab, characterized in that: The base film (1) includes a base film (1) with a metal foil (2) at its end. In a direction perpendicular to the metal foil (2) along the base film (1), the base film (1) includes a first region closest to the metal foil (2) and a second region farthest from the metal foil (2). Both the first region and the second region are provided with a plurality of holes (6) penetrating the thickness of the base film (1). The density of the holes (6) in the first region is greater than the density of the holes (6) in the second region. The base film (1) and the metal foil (2) are provided with a base layer (4) and a metal layer (5) in sequence on their sides to connect the base film (1) and the metal foil (2) into one unit.

2. The low-resistance composite current collector with pre-installed integrated electrode tab according to claim 1, characterized in that: The density of holes (6) in the first region is set to 2,000-50,000 per square centimeter, and the density of holes (6) in the second region is set to 50-2,000 per square centimeter.

3. The low-resistance composite current collector with pre-installed integrated electrode tab according to claim 1, characterized in that: A third region is provided between the first region and the second region. The third region is provided with multiple rows of holes (6). The density of the holes (6) in the third region is less than the density of the holes (6) in the first region but greater than the density of the holes (6) in the second region.

4. The low-resistance composite current collector with pre-installed integrated electrode tab according to claim 1, characterized in that: The base film (1) and the metal foil (2) are provided with the underlayment (4) and the metal layer (5) on each side. The underlayment (4) and the metal layer (5) cover the inner wall of the hole (6) to connect the underlayment (4) and the metal layer (5) located on the two opening surfaces of the hole (6).

5. A method for preparing a low-resistance composite current collector with a pre-embedded integrated tab as described in any one of claims 1-4, characterized in that: This includes gradient perforation of the first, second and third regions on the base film (1), attaching the metal foil (2) with adhesive layer (3) to the tab region on the base film (1), and then depositing the underlayer (4) and metal layer (5) on the sides of the base film (1) and the metal foil (2).

6. The method according to claim 5, characterized in that: A laser is used to perform gradient laser drilling on the first, second and third regions of the base film (1).

7. The method according to claim 6, characterized in that: When drilling holes in the first region, the laser beam is controlled to perform scanning drilling at a pulse frequency of 200-500 kHz and a scanning interval of 5-10 μm.

8. The method according to claim 7, characterized in that: When drilling holes in the second region, the laser beam is controlled to perform scanning drilling at a pulse frequency of 50-150 kHz and a scanning interval of 50-100 μm.

9. The method according to claim 8, characterized in that: When drilling holes in the third region, the laser beam is controlled to scan and drill holes along the direction from the first region to the second region, with the scanning spacing of the first region gradually increasing to the scanning spacing of the second region.

10. The method according to claim 6, characterized in that: The pulse energy of the laser is 0.1-2 mJ.

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